filters.approximatecoplanar¶
The approximate coplanar filter implements a portion of the algorithm presented in [Limberger2015]. Prior to clustering points, the authors first apply an approximate coplanarity test, where points that meet the following criteria are labeled as approximately coplanar.
\(\lambda_1\), \(\lambda_2\), \(\lambda_3\) are the eigenvalues of
a neighborhood of points (defined by knn
nearest neighbors) in ascending
order. The threshold values \(s_{\alpha}\) and \(s_{\beta}\) are
user-defined and default to 25 and 6 respectively.
The filter returns a point cloud with a new dimension Coplanar
that
indicates those points that are part of a neighborhood that is approximately
coplanar (1) or not (0).
Example¶
The sample pipeline presented below estimates the planarity of a point based on its eight nearest neighbors using the approximate coplanar filter. A filters.range stage then filters out any points that were not deemed to be coplanar before writing the result in compressed LAZ.
[
"input.las",
{
"type":"filters.approximatecoplanar",
"knn":8,
"thresh1":25,
"thresh2":6
},
{
"type":"filters.range",
"limits":"Coplanar[1:1]"
},
"output.laz"
]
Options¶
- knn
The number of k-nearest neighbors. [Default: 8]
- thresh1
The threshold to be applied to the smallest eigenvalue. [Default: 25]
- thresh2
The threshold to be applied to the second smallest eigenvalue. [Default: 6]